BaseTools/Source/C/BrotliCompress/enc/quality.h

   1 /* Copyright 2016 Google Inc. All Rights Reserved.
   2
   3    Distributed under MIT license.
   4    See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
   5 */
   6
   7 /* Constants and formulas that affect speed-ratio trade-offs and thus define
   8    quality levels. */
   9
  10 #ifndef BROTLI_ENC_QUALITY_H_
  11 #define BROTLI_ENC_QUALITY_H_
  12
  13 #include "../common/platform.h"
  14 #include <brotli/encode.h>
  15 #include "./params.h"
  16
  17 #define FAST_ONE_PASS_COMPRESSION_QUALITY 0
  18 #define FAST_TWO_PASS_COMPRESSION_QUALITY 1
  19 #define ZOPFLIFICATION_QUALITY 10
  20 #define HQ_ZOPFLIFICATION_QUALITY 11
  21
  22 #define MAX_QUALITY_FOR_STATIC_ENTROPY_CODES 2
  23 #define MIN_QUALITY_FOR_BLOCK_SPLIT 4
  24 #define MIN_QUALITY_FOR_NONZERO_DISTANCE_PARAMS 4
  25 #define MIN_QUALITY_FOR_OPTIMIZE_HISTOGRAMS 4
  26 #define MIN_QUALITY_FOR_EXTENSIVE_REFERENCE_SEARCH 5
  27 #define MIN_QUALITY_FOR_CONTEXT_MODELING 5
  28 #define MIN_QUALITY_FOR_HQ_CONTEXT_MODELING 7
  29 #define MIN_QUALITY_FOR_HQ_BLOCK_SPLITTING 10
  30
  31 /* For quality below MIN_QUALITY_FOR_BLOCK_SPLIT there is no block splitting,
  32    so we buffer at most this much literals and commands. */
  33 #define MAX_NUM_DELAYED_SYMBOLS 0x2FFF
  34
  35 /* Returns hash-table size for quality levels 0 and 1. */
  36 static BROTLI_INLINE size_t MaxHashTableSize(int quality) {
  37   return quality == FAST_ONE_PASS_COMPRESSION_QUALITY ? 1 << 15 : 1 << 17;
  38 }
  39
  40 /* The maximum length for which the zopflification uses distinct distances. */
  41 #define MAX_ZOPFLI_LEN_QUALITY_10 150
  42 #define MAX_ZOPFLI_LEN_QUALITY_11 325
  43
  44 /* Do not thoroughly search when a long copy is found. */
  45 #define BROTLI_LONG_COPY_QUICK_STEP 16384
  46
  47 static BROTLI_INLINE size_t MaxZopfliLen(const BrotliEncoderParams* params) {
  48   return params->quality <= 10 ?
  49       MAX_ZOPFLI_LEN_QUALITY_10 :
  50       MAX_ZOPFLI_LEN_QUALITY_11;
  51 }
  52
  53 /* Number of best candidates to evaluate to expand Zopfli chain. */
  54 static BROTLI_INLINE size_t MaxZopfliCandidates(
  55   const BrotliEncoderParams* params) {
  56   return params->quality <= 10 ? 1 : 5;
  57 }
  58
  59 static BROTLI_INLINE void SanitizeParams(BrotliEncoderParams* params) {
  60   params->quality = BROTLI_MIN(int, BROTLI_MAX_QUALITY,
  61       BROTLI_MAX(int, BROTLI_MIN_QUALITY, params->quality));
  62   if (params->quality <= MAX_QUALITY_FOR_STATIC_ENTROPY_CODES) {
  63     params->large_window = BROTLI_FALSE;
  64   }
  65   if (params->lgwin < BROTLI_MIN_WINDOW_BITS) {
  66     params->lgwin = BROTLI_MIN_WINDOW_BITS;
  67   } else {
  68     int max_lgwin = params->large_window ? BROTLI_LARGE_MAX_WINDOW_BITS :
  69                                            BROTLI_MAX_WINDOW_BITS;
  70     if (params->lgwin > max_lgwin) params->lgwin = max_lgwin;
  71   }
  72 }
  73
  74 /* Returns optimized lg_block value. */
  75 static BROTLI_INLINE int ComputeLgBlock(const BrotliEncoderParams* params) {
  76   int lgblock = params->lgblock;
  77   if (params->quality == FAST_ONE_PASS_COMPRESSION_QUALITY ||
  78       params->quality == FAST_TWO_PASS_COMPRESSION_QUALITY) {
  79     lgblock = params->lgwin;
  80   } else if (params->quality < MIN_QUALITY_FOR_BLOCK_SPLIT) {
  81     lgblock = 14;
  82   } else if (lgblock == 0) {
  83     lgblock = 16;
  84     if (params->quality >= 9 && params->lgwin > lgblock) {
  85       lgblock = BROTLI_MIN(int, 18, params->lgwin);
  86     }
  87   } else {
  88     lgblock = BROTLI_MIN(int, BROTLI_MAX_INPUT_BLOCK_BITS,
  89         BROTLI_MAX(int, BROTLI_MIN_INPUT_BLOCK_BITS, lgblock));
  90   }
  91   return lgblock;
  92 }
  93
  94 /* Returns log2 of the size of main ring buffer area.
  95    Allocate at least lgwin + 1 bits for the ring buffer so that the newly
  96    added block fits there completely and we still get lgwin bits and at least
  97    read_block_size_bits + 1 bits because the copy tail length needs to be
  98    smaller than ring-buffer size. */
  99 static BROTLI_INLINE int ComputeRbBits(const BrotliEncoderParams* params) {
 100   return 1 + BROTLI_MAX(int, params->lgwin, params->lgblock);
 101 }
 102
 103 static BROTLI_INLINE size_t MaxMetablockSize(
 104     const BrotliEncoderParams* params) {
 105   int bits =
 106       BROTLI_MIN(int, ComputeRbBits(params), BROTLI_MAX_INPUT_BLOCK_BITS);
 107   return (size_t)1 << bits;
 108 }
 109
 110 /* When searching for backward references and have not seen matches for a long
 111    time, we can skip some match lookups. Unsuccessful match lookups are very
 112    expensive and this kind of a heuristic speeds up compression quite a lot.
 113    At first 8 byte strides are taken and every second byte is put to hasher.
 114    After 4x more literals stride by 16 bytes, every put 4-th byte to hasher.
 115    Applied only to qualities 2 to 9. */
 116 static BROTLI_INLINE size_t LiteralSpreeLengthForSparseSearch(
 117     const BrotliEncoderParams* params) {
 118   return params->quality < 9 ? 64 : 512;
 119 }
 120
 121 static BROTLI_INLINE void ChooseHasher(const BrotliEncoderParams* params,
 122                                        BrotliHasherParams* hparams) {
 123   if (params->quality > 9) {
 124     hparams->type = 10;
 125   } else if (params->quality == 4 && params->size_hint >= (1 << 20)) {
 126     hparams->type = 54;
 127   } else if (params->quality < 5) {
 128     hparams->type = params->quality;
 129   } else if (params->lgwin <= 16) {
 130     hparams->type = params->quality < 7 ? 40 : params->quality < 9 ? 41 : 42;
 131   } else if (params->size_hint >= (1 << 20) && params->lgwin >= 19) {
 132     hparams->type = 6;
 133     hparams->block_bits = params->quality - 1;
 134     hparams->bucket_bits = 15;
 135     hparams->hash_len = 5;
 136     hparams->num_last_distances_to_check =
 137         params->quality < 7 ? 4 : params->quality < 9 ? 10 : 16;
 138   } else {
 139     hparams->type = 5;
 140     hparams->block_bits = params->quality - 1;
 141     hparams->bucket_bits = params->quality < 7 ? 14 : 15;
 142     hparams->num_last_distances_to_check =
 143         params->quality < 7 ? 4 : params->quality < 9 ? 10 : 16;
 144   }
 145
 146   if (params->lgwin > 24) {
 147     /* Different hashers for large window brotli: not for qualities <= 2,
 148        these are too fast for large window. Not for qualities >= 10: their
 149        hasher already works well with large window. So the changes are:
 150        H3 --> H35: for quality 3.
 151        H54 --> H55: for quality 4 with size hint > 1MB
 152        H6 --> H65: for qualities 5, 6, 7, 8, 9. */
 153     if (hparams->type == 3) {
 154       hparams->type = 35;
 155     }
 156     if (hparams->type == 54) {
 157       hparams->type = 55;
 158     }
 159     if (hparams->type == 6) {
 160       hparams->type = 65;
 161     }
 162   }
 163 }
 164
 165 #endif  /* BROTLI_ENC_QUALITY_H_ */